This invention relates to bushes for between a shaft and a housing surrounding said shaft.
The invention is particularly applicable to bushes for brake shafts in air or vacuum brakes, such as those used in heavy transport vehicles, and will be described in relation to this.
Such air-pressure or vacuum brakes are well-known. In their usual form, a linkage operated by the air source turns a brake shaft which moves the brake shoes to or from the brake drum.
The actuating shaft is supported in a bush mounted in a housing to maintain the shaft axis accurately in position. The usual prior-art bush has consisted of a two-part structure, the parts when together forming a bobbin with the parts abutting along the transverse centre plane of the bobbin. The bobbin is mounted with the end plates of the housing adjacent the ends of the bobbin but with a designed clearance therefrom.
Such a bobbin cannot be made a tight fit in the housing endwise, and movements of it during brake operation result in rapid wear of the housing and of the shaft. A further disadvantage is that considerable labour time is needed is dismantling the housing and shaft for repairs.